Two defense officials said that the Navy tried to contact the Russian aircraft by radio but there was no response. The U.S. vessel did not take any evasive action.

Cap. Danny Hernandez, the spokesman for U.S. European Command, called Friday's incidents “unsafe and unprofessional” due to the speed and distance of the aircraft from the ship.

All four Russian planes were flying without their transponders on, the U.S. officials said. Transponders help identify an aircraft, and American officials say flying with the transponders off increased the risk of an accident or miscalculation.

American officials said the USS Porter was conducting routine operations in international waters.